Data communication system with increased effective bandwidth

A communication system for interconnecting a plurality of user devices having means for transmitting signals to and receiving signals from said communications system, and communication system having means for providing a plurality of frequency multiplexed communication channels operating on different frequency bands for concurrent communication between said user devices, the communication system having a network with a medium comprising a receive branch and a transmit branch, the receive branch transmitting signals in the direction away from a head end and the transmit branch transmitting signals in the direction towards the head end, the branches being connected at the head end to pass signals from the transmit branch to the receive branch,

• wherein one or more but not all of said channels are dedicated as local service channels employing designated local frequencies, and said system includes frequency selective isolation means connected into said network intermediately between user devices, thereby subdividing said network into a plurality of subnets, each subnet interconnecting a plurality of said user devices,
• each said frequency selective isolation means being connected into the network with connections to both the receive branch and the transmit branch looking towards the head end, and to both the receive branch and to the transmit branch looking away from the head end,
• each said frequency selected isolation means including
• means for reemitting on the receive branch in the direction away from the head end signals on said local frequencies entering the frequency selected isolation means on the transmit branch from the direction away from the head end, and
• means for reemitting on the receive branch in the direction away from the head end signals on other than local frequencies entering the frequency selected isolations means on the receive branch from the head end direction,
• means for reemitting on the transmit branch in the direction toward the head end signals on other than local frequencies entering the frequency selected isolations means on the transmit branch from the direction away from the head end,
• means for blocking signals on local frequencies from transmission between one subnet and another,
• said communication system providing communications on a particular one of said local frequencies between two of said user devices both connected on a first of said subnets while concurrently and without interference providing communications on the same particular local frequency between two of said user devices both connected on a second of said subnets, while concurrently and without interference providing communications on a frequency other than local frequencies between user devices connected on different subnets.

A combination, including

• a communications subnet for connection to a communication system at a junction point, said subnet interconnecting a plurality of user devices having means for transmitting signals to and receiving signals from said communications system, the subnet and the communications system having a communications medium comprising a receive branch and a transmit branch, the receive branch of the subnet transmitting signals in the direction junction point-toward-user devices and the transmit branch of the subnet transmitting signals in the direction user devices-towards-junction point, and
• an interfacing device interfacing the subnet to the communication system, said interfacing device including
• means for receiving signals on predesignated local frequencies from the transmit branch of the subnet and reemitting them onto the receive branch of the subnet,
• means for receiving signals on other than said predesignated local frequencies from the transmit branch of the subnet and reemitting them onto the transmit branch of the communications system,
• means for receiving signals on other than said predesignated local frequencies from the receive branch of the communications system and reemitting them onto the receive branch of the communications system,
• means for blocking signals on said predesignated local frequencies from being transmitted between the subnet and the communications system,
• said combination providing communications on said local frequencies between user devices both connected on said subnet without interferring with communications of user devices both connected elsewhere in said communications system and using the same local frequency, and further providing communications on frequencies other than said local frequencies between a user device connected on said subnet and user devices of the communication system connected elsewhere than on said subnet.